Although domestic waterborne ton-miles and tonnage declined over the last two decades (see table), there were overall increases in value, tons, and ton-miles as U.S. international trade grew during this period. Today, maritime transportation carries nearly 80 percent of the tonnage of U.S. import and export freight.

From 1993 to 2002, the value per ton of waterborne freight increased from $290 to $370 (see figure), reflecting the rising reliance on imports for manufactured goods (e.g., high-value automobiles and automotive parts from Europe and Asia). And the total tonnage of domestic and international trade traveling U.S. waters increased more than 10 percent, from 2 billion tons in 1993 to 2.3 billion tons in 2002.